Myocardial fibrosis is a morphologic change common to multiple cardiac disease conditions. In addition to replacement (scar) fibrosis, there is increasing recognition of interstitial (reactive) fibrosis being an important player in structural remodeling of the diseased heart, as well as the genesis of fatal arrhythmia leading to sudden cardiac death. Currently, fibrosis is quantified by histochemical analysis of tissue samples obtained by surgical biopsy. The availability of a non-invasive test to quantify replacement and interstitial fibrosis, which may be correlated with the collagen volume fraction (CVF), would be a significant advance.